kc3-lang/libtommath

diff --git a/README.md b/README.md
index 0e57a4d..647e179 100644
--- a/README.md
+++ b/README.md
@@ -23,3 +23,7 @@ The project can be build by using `make`. Along with the usual `make`, `make cle
 Tests are located in `demo/` and can be built in two flavors.
 * `make test` creates a test binary that is intended to be run against `mtest`. `mtest` can be built with `make mtest` and test execution is done like `./mtest/mtest | ./test`. `mtest` is creating test vectors using an alternative MPI library and `test` is consuming these vectors to verify correct behavior of ltm
 * `make test_standalone` creates a stand-alone test binary that executes several test routines.
+
+## Building and Installing
+
+Building is straightforward for GNU Linux only, the section "Building LibTomMath" in the documentation in `doc/bn.pdf` has the details.
diff --git a/doc/bn.tex b/doc/bn.tex
index 88b1954..533c623 100644
--- a/doc/bn.tex
+++ b/doc/bn.tex
@@ -97,7 +97,20 @@ public domain everyone is entitled to do with them as they see fit.
 
 LibTomMath is meant to be very ``GCC friendly'' as it comes with a makefile well suited for GCC.  However, the library will
 also build in MSVC, Borland C out of the box.  For any other ISO C compiler a makefile will have to be made by the end
-developer.
+developer. Please consider to commit such a makefile to the LibTomMath developers, currently residing at
+\url{http://github.com/libtom/libtommath}, if successfully done so.
+
+Intel's C-compiler (ICC) is sufficiently compatible with GCC, at least the newer versions, to replace GCC for building the static and the shared library. Editing the makfiles is not needed, just set the shell variable \texttt{CC} as shown below.
+\begin{alltt}
+CC=/home/czurnieden/intel/bin/icc make
+\end{alltt}
+
+ICC does not know all options available for GCC and LibTomMath uses two diagnostics \texttt{-Wbad-function-cast} and \texttt{-Wcast-align} that are not supported by ICC resulting in the warnings:
+\begin{alltt}
+icc: command line warning #10148: option '-Wbad-function-cast' not supported
+icc: command line warning #10148: option '-Wcast-align' not supported
+\end{alltt}
+It is possible to mute this ICC warning with the compiler flag \texttt{-diag-disable=10006}\footnote{It is not recommended to suppress warnings without a very good reason but there is no harm in doing so in this very special case.}.
 
 \subsection{Static Libraries}
 To build as a static library for GCC issue the following
@@ -115,6 +128,7 @@ This will build the library and archive the object files in ``tommath.lib''.  Th
 version 6.00 with service pack 5.
 
 \subsection{Shared Libraries}
+\subsubsection{GNU based Operating Systems}
 To build as a shared library for GCC issue the following
 \begin{alltt}
 make -f makefile.shared
@@ -123,10 +137,70 @@ This requires the ``libtool'' package (common on most Linux/BSD systems).  It wi
 and static then install (by default) into /usr/lib as well as install the header files in /usr/include.  The shared
 library (resource) will be called ``libtommath.la'' while the static library called ``libtommath.a''.  Generally
 you use libtool to link your application against the shared object.
-
+\subsubsection{Microsoft Windows based Operating Systems}
 There is limited support for making a ``DLL'' in windows via the ``makefile.cygwin\_dll'' makefile.  It requires
 Cygwin to work with since it requires the auto-export/import functionality.  The resulting DLL and import library
 ``libtommath.dll.a'' can be used to link LibTomMath dynamically to any Windows program using Cygwin.
+\subsubsection{OpenBSD}
+OpenBSD replaced some of their GNU-tools, especially \texttt{libtool} with their own, slightly different versions. To ease the workload of LibTomMath's developer team, only a static library can be build with the included \texttt{makefile.unix}.
+
+The wrong \texttt{make} will result in errors like:
+\begin{alltt}
+*** Parse error in /home/user/GITHUB/libtommath: Need an operator in 'LIBNAME' )
+*** Parse error: Need an operator in 'endif' (makefile.shared:8)
+*** Parse error: Need an operator in 'CROSS_COMPILE' (makefile_include.mk:16)
+*** Parse error: Need an operator in 'endif' (makefile_include.mk:18)
+*** Parse error: Missing dependency operator (makefile_include.mk:22)
+*** Parse error: Missing dependency operator (makefile_include.mk:23)
+...
+\end{alltt}
+The wrong \texttt{libtool} will build it all fine but when it comes to the final linking fails with
+\begin{alltt}
+...
+cc -I./ -Wall -Wsign-compare -Wextra -Wshadow -Wsystem-headers -Wdeclaration-afo...
+cc -I./ -Wall -Wsign-compare -Wextra -Wshadow -Wsystem-headers -Wdeclaration-afo...
+cc -I./ -Wall -Wsign-compare -Wextra -Wshadow -Wsystem-headers -Wdeclaration-afo...
+libtool --mode=link --tag=CC cc  bn_error.lo bn_fast_mp_invmod.lo bn_fast_mp_mo 
+libtool: link: cc bn_error.lo bn_fast_mp_invmod.lo bn_fast_mp_montgomery_reduce0
+bn_error.lo: file not recognized: File format not recognized
+cc: error: linker command failed with exit code 1 (use -v to see invocation)
+Error while executing cc bn_error.lo bn_fast_mp_invmod.lo bn_fast_mp_montgomery0
+gmake: *** [makefile.shared:64: libtommath.la] Error 1
+\end{alltt}
+
+To build a shared library with OpenBSD\footnote{Tested with OpenBSD version 6.4} the GNU versions of \texttt{make} and \texttt{libtool} are needed.
+\begin{alltt}
+$ sudo pkg_add gmake libtool
+\end{alltt}
+At this time two versions of \texttt{libtool} are installed and both are named \texttt{libtool}, unfortunately but GNU \texttt{libtool} has been placed in \texttt{/usr/local/bin/} and the native version in \texttt{/usr/bin/}. The path might be different in other versions of OpenBSD but both programms differ in the output of \texttt{libtool --version}
+\begin{alltt}
+$ /usr/local/bin/libtool --version                              
+libtool (GNU libtool) 2.4.2
+Written by Gordon Matzigkeit <gord@gnu.ai.mit.edu>, 1996
+
+Copyright (C) 2011 Free Software Foundation, Inc.
+This is free software; see the source for copying conditions.  There is NO
+warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+$ libtool --version
+libtool (not (GNU libtool)) 1.5.26
+\end{alltt}
+
+The shared library should build now with
+\begin{alltt}
+LIBTOOL="/usr/local/bin/libtool" gmake -f makefile.shared
+\end{alltt}
+You might need to run a \texttt{gmake -f makefile.shared clean} first.
+
+\subsubsection{NetBSD}
+NetBSD is not as strict as OpenBSD but still needs \texttt{gmake} to build the shared library. \texttt{libtool} may also not exist in a fresh install.
+\begin{alltt}
+pkg_add gmake libtool
+\end{alltt}
+Please check with \texttt{libtool --version} that installed libtool is indeed a GNU libtool.
+Build the shared library by typing:
+\begin{alltt}
+gmake -f makefile.shared
+\end{alltt}
 
 \subsection{Testing}
 To build the library and the test harness type
diff --git a/makefile_include.mk b/makefile_include.mk
index 5ebcd5d..f29d7be 100644
--- a/makefile_include.mk
+++ b/makefile_include.mk
@@ -92,7 +92,7 @@ endif
 ifeq ($(PLATFORM),FreeBSD)
   _ARCH := $(shell sysctl -b hw.machine_arch)
 else
-  _ARCH := $(shell arch)
+  _ARCH := $(shell uname -m)
 endif
 
 # adjust coverage set